1. Field of the Invention
This invention relates to high speed shears of the type employed to trim the front and tail ends of hot rolled steel rods and other like products moving at speeds exceeding 100 m/sec.
2. Description of the Prior Art
In order to reliably trim both the front and tail ends of rods traveling at the high delivery speeds of modem rolling mills, which are now reaching 120 m/sec., the shear blades must rotate continuously at speeds synchronized with mill delivery speeds, and they must be arranged for precise coordinated movement into and out of cutting positions during extremely brief time intervals of less than about 6 milliseconds. The shears of the prior art have various shortcomings which inhibit their ability to meet these challenges.
For example, as disclosed in U.S. Pat. No. 2,451,948 (Hawthorne); U.S. Pat. No. 3,057,239 (Teplitz); U.S. Pat. No. 4,027,565 (Elsner et al.); and U.S. Pat. No. 4,640,164 (Pavlov), various schemes have been developed to effect radial adjustment of the cutting blades with respect to rotatable blade holders. These arrangements are mechanically complex, difficult to coordinate and control precisely, and are thus not suitable for very high speed operations of the type contemplated by the present invention.
Other known shears, as disclosed for example by U.S. Pat. No. 3,561,311 (Nowak); U.S. Pat. No. 4,058,041 (Ito); U.S. Pat. No. 4,656,905 (Ginzburg et al.); and U.S. Pat. No. 5,027,138 (Sato et al.) shift one or both of the rotating blade holders, either radially or axially, into and out of cutting positions. Although these arrangements avoid the complexities associated with radial blade adjustments, the inertias inherent in their adjustment mechanisms inhibit their ability to respond with sufficient rapidity.
The objective of the present invention is to provide an improved shear which is free of the disadvantages of the prior art, and capable of operating at the high delivery speeds of modern rod mills.